JPH0443955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering heat from tar-containing high-temperature gases, particularly those generated by high-temperature treatment of fossil fuels such as coke oven crude gas, coal pyrolysis gas, vacuum residual partially combusted gas, etc. This invention relates to a method for recovering heat from tar-containing high-temperature gas.

Conventionally, the crude gas generated in the Cooss furnace was cooled by flushing with ammonium water and then transferred to the gas purification process, and the sensible heat of this gas was discarded without being utilized.

Therefore, an attempt was made to recover the sensible heat by introducing the coke-generated crude gas into a shell-and-tube heat exchanger, but the coke oven-generated crude gas contains low-boiling point substances such as benzol and high-boiling point substances such as tar. At temperatures above 450°C, carbon produced by high-temperature decomposition of tar will be deposited on the surface of the heat transfer tube, and at temperatures below 450°C, high-boiling substances such as tar will be transferred. condenses on the heat tube surface,
At temperatures below 100°C naphthalene and other soluble substances condense on the tube surface. As a result, the gas flow path is blocked by these carbons and condensates, causing so-called coking, which increases pressure loss in the gas flow and reduces heat exchange efficiency, making it difficult to operate the equipment stably for long periods of time. becomes difficult.

In addition, attempts have been made to spray high-boiling point oil such as tar distilled from coke oven crude gas and bring it into direct contact with the crude gas, thereby exchanging heat and recovering the sensible heat. Since the gas contains naphthalene and other soluble substances and dust, these can mix into high-boiling point oils such as tar, clogging high-boiling point oil injection nozzles and clogging high-boiling point oil circulation lines. , decomposition and deterioration of high boiling point oils occur, making it difficult to operate the equipment stably for long periods of time.

The present invention was invented in view of the above, and
The purpose is to sufficiently recover the sensible heat of high-temperature gases containing high-boiling substances such as tar, naphthalene and other soluble substances, dust, etc., and to improve the heat recovery rate. Another object of the present invention is to recover the sensible heat of this type of gas as heat in a high temperature range, thereby improving its range of use and value. A further object of the present invention is to
The purpose is to enable stable operation of the equipment for long periods of time. Still another object of the present invention is to make the tar cooler smaller and more efficient, and to reduce the driving power of the tar circulation pump. Still another object of the present invention is to provide a spouted bed cooler that heats a liquid heat medium through solid particles that are in direct contact with a tar-containing hot gas, and a circulating tar that is in direct contact with carbon powder and gas flowing out from the spouted bed cooler. A first tar cooler that heats the liquid heat medium through the first tar cooler, and a second tar cooler that exchanges heat between the gas flowing out from the first tar cooler and the liquid heat medium and sprays light tar into the cooled gas. the remaining tar circulating in the first tar cooler is extracted, the remaining light tar circulating in the second tar cooler is extracted, and a part of the extracted light tar is circulated in the first tar cooler. The liquid heat medium mixed in the tar and preheated by the second tar cooler is introduced into the first tar cooler, and the liquid heat medium heated by the first tar cooler is further introduced into the high-temperature spouted bed cooler. The present invention provides a method for recovering heat from tar-containing high-temperature gas, which comprises heating the tar-containing high-temperature gas. Other advantages and features of the invention will become clearer from the following drawings showing exemplary embodiments and the description thereof.

FIG. 1 is a schematic system diagram of one embodiment of the present invention. High temperature (approximately 600°C to 800°C) coke oven generated crude gas _G1 is introduced into the spouted bed cooler 1 from its inlet nozzle, and while rising in the draft pipe 2 with solid particles a, the heat is transferred to the solid particles. At the same time, tar and pitch in the gas condense on the surfaces of particles a. Then, the gas that has ascended through the draft pipe 2 collides with the collision plate 3 and is separated from the solid particles a. The solid particles a that collided with the collision plate 3 fall around the heat exchanger tube 4, and the liquid heat medium flowing inside the heat exchanger tube 4,
That is, the water is heated and cooled, and at the same time, the tar and pitch condensed on its outer surface are carbonized and become carbon powder.The solid particles a, which have been cooled by applying heat to the water, are then separated by collisions between the particles a. It rises in the draft pipe 2 accompanied by the gas G ₁ flowing in from the inlet nozzle. The gas _G2 , which has been cooled to about 400 to 500°C in the spouted bed cooler 1, flows into the gas-liquid contact chamber 11 above the wet wall tar cooler 5, accompanied by carbon powder, where it is connected to the spray nozzle. 1
At the same time, the carbon powder in the gas and the cooled and condensed tar and pitch droplets are adsorbed and collected by the circulating tar. When the circulating tar turns into a thin liquid film and descends along the inner surface of the vertical heat exchanger tube 12, it gives heat to the water outside the vertical heat exchanger tube 12 and enters the gas-liquid separation chamber 13. Here, the gas is separated from the circulating tar and flows out as gas _G3 with a temperature of about 200° to 300°C. The tar separated in the gas-liquid separation chamber 13 is extracted by a tar circulation pump 14,
Most of the tar is circulated through the tar circulation pipe 15 to the spray nozzle 10. The remainder is extracted from the system through the tar extraction pipe 21. tar cooler 5
The gas _G3 flowing out from the indirect contact heat exchanger 16
The water flowing outside the heat exchanger tube 17 is cooled by being guided to the upper inlet chamber of the tube, and in the process of descending through the vertical heat exchanger tube 17, is cooled.
8, and here, after the light tar in the gas condensed by being cooled is brought into contact with the light tar sprayed from the nozzle 19 and separated, 80 to 120
It flows out as gas _G4 at ℃. Lower outlet quality 18
The light low boiling point tar separated is extracted by the tar pump 20, and a part of it is passed through the nozzle
9 and is recirculated, but part of it is returned as diluted tar to the separated substance 13 of the tar cooler 5 via the diluted tar supply pipe 28, and the remaining surplus is taken out of the system through the extraction pipe 22. It will be done. The gas G ₄ flowing out from the indirect contact heat exchanger 16 is guided to the air-water contact tank 26 , where it is cooled by contacting water sprayed from the nozzle 25 , and then transferred to the gas-liquid separation tank 2 .
Gas G ₅ flows into G 7 and is separated from water droplets here.
is discharged through the exhaust fan 29. The water separated in the gas-liquid separation tank is extracted and discharged by the pump 30. When the water supplied by the water supply pump 9 passes through the piping 23 and outside the vertical heat exchanger tubes 17 of the indirect contact heat exchanger 16, it is heated by the gas passing through the heat exchanger tubes 17, and then passes through the piping 24. The brackish water is then supplied to the brackish water drum 7. The water separated from the steam in the brackish water drum 7 is extracted by the pump 6.
When flowing through the heat exchanger tubes 4 of the spouted bed cooler 1, the solid particles a absorb heat from the solid particles a outside the heat exchanger tubes 4, are heated, and return to the brackish water drum 7. The remainder of the water extracted by the pump 6 is guided outside the vertical heat exchanger tube 12 of the tar cooler 5, exchanges heat with the gas flowing through the heat exchanger tube 12, and is heated, and then returns to the brackish water drum 7. The water returned to the brackish water drum 7 is flash evaporated here because the pressure inside the brackish water drum 7 is below the saturated vapor pressure, and the steam is supplied to the user through the steam pipe 8.

The coke oven generated crude gas _G1 , which is at a high temperature of about 600° to 1000°C, is first sent to the spouted bed cooler 1, where it is cooled to about 400° to 550°C. High boiling point substances are solid particles 9
After condensing on the surface of the heat exchanger tube 4, the solid particles a are carbonized as they descend, and further peeled off due to collisions with each other, so that the condensate of these high boiling point substances or their carbide adheres to the heat exchanger tube 4, causing Heat exchange efficiency is not inhibited, and the solid particles a are automatically regenerated, so they can be recycled and used. Incidentally, if the gas is cooled too much by the spouted bed cooler 1, the amount of tar condensed increases and the diameter of the solid particles a increases or their aggregation occurs, so the cooling temperature of the gas is preferably 450° C. or higher. Spouted bed cooler 1 is installed in tar cooler 5.
Gas cooled at about 400℃ to 500℃ is introduced, so even if tar and pitches in the gas condense, they can be washed away with a large amount of circulating tar, so coking with these condensates can be avoided. will never occur. Furthermore, the circulating tar is supplemented with light, low-boiling point tar condensed in the indirect contact heat exchanger 16 to keep its viscosity low, so the thickness of the liquid film flowing down inside the heat transfer tubes 12 is thin. Therefore, the cooling performance can be improved and the driving power of the tar pump 14 can be reduced. In addition,
The tar contained in the crude gas generated from a coke oven is 425℃
Condensation starts at 200℃, and the tar condensation rate is about 50%.
reach. Therefore, it is appropriate to introduce gas at a temperature of 425° C. or lower into the tar cooler 5. The indirect contact heat exchanger 16 has a tar cooler 5 with a temperature of 200°
Since gas _G3 cooled to 300°C is introduced, coking and tar sticking to the heat exchanger tubes no longer occur in this temperature range. And this heat exchanger 1
By cooling the gas G ₃ at 200°C to 300°C to 80°C to 120°C in Step 6, the heat medium to be supplied to the spouted bed cooler 1 and the tar cooler 5 is generated using the heat of the gas corresponding to the temperature difference in this low temperature region. It can be recovered by preheating. In other words, the relationship between the amount of steam generated and the cooling temperature when processing 30,000 Nm ³ /H of crude gas generated from a coke oven at 600°C is shown in Figure 2.
The amount of steam recovered when cooled to ℃ is 7.3TON/H.
However, by further cooling this to 100° C. using the indirect contact heat exchanger 16, the amount of steam recovered becomes 10 TON/H, which is an improvement of 45%. Figure 3 shows the relationship between the cooling temperature, tar viscosity, and carbon powder concentration in the tar cooler 5, and the carbon powder concentration b when diluted tar is supplied is compared to the carbon powder concentration a when diluted tar is not supplied. The tar viscosity d when diluted tar is supplied is much lower than the tar viscosity c when diluted tar is not supplied. In addition, FIG. 4 shows the relationship between the distillation temperature and the distillation amount, and T is the amount of tar in the extraction pipe 22 when the outlet gas temperature of the indirect contact heat exchanger 16 is operated at 80°C. It is a distillation curve, and P is the extraction pipe 2 when the outlet gas temperature of the tar cooler 5 is operated at 250°C.
This is a distillation curve of tar in No. 1, and as is clear from the graph, it can be seen that the distillate fraction above 400°C and the distillate fraction below 400°C are separated and recovered. In the above embodiment, an example was explained in which a wet wall heat exchanger was adopted as the tar cooler. A tar quencher having a cooling section can be used. In FIG. 5, gas _G3 supplied from the spouted bed cooler enters the gas-liquid contactor 31,
Here, after being cooled by contacting with the circulating tar droplets sprayed from the spray nozzle 32, the gas-liquid separation tank 34
After decomposing the tar droplets in the gas, the gas is sent from the outlet 35 to the next indirect contact heat exchanger. The tar separated in the gas-liquid separation tank 34 is extracted by a pump 37 and sent to a heat exchanger 38, where it is cooled by applying heat to water 39, which is a liquid heat medium. It is sprayed from the spray nozzle 32, and a part of it is extracted from the extraction pipe 41. The water heated by the heat exchanger 38 is supplied to the brackish water drum. Furthermore, although water is used as the heat medium in the above embodiments, it goes without saying that heat-resistant oil or other liquid heat medium may be used.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

Figure 1 shows one embodiment of the present invention and a diagrammatic system diagram;
The figure is a diagram showing the relationship between cooling temperature and amount of steam generated.
Figure 3 is a diagram showing the relationship between cooling temperature, carbon powder concentration, and tar viscosity in a tar cooler;
Figure 4 is a diagram showing the relationship between distillation temperature and distillation amount;
FIG. 5 is a schematic system diagram showing another example of the tar cooler. Tar-containing high-temperature gas...G ₁ , spouted bed cooler...
...1, Tar cooler...5, Indirect contact heat exchanger...16, Dilution tar supply pipe...28.

Claims (1)

[Claims] 1. A spouted bed cooler that heats a liquid heat medium through solid particles that are in direct contact with a tar-containing high-temperature gas;
A first tar cooler that heats a liquid heat medium through circulating tar that is in direct contact with the carbon powder and gas flowing out from the spouted bed cooler, and a heat exchanger between the gas flowing out from the first tar cooler and the liquid heat medium. and a second tar cooler that sprays light tar into the cooled gas, extracting the remainder of the tar circulating in the first tar cooler, extracting the remainder of the light tar circulating in the second tar cooler, and , a part of the extracted light tar is mixed into the circulating tar of the first tar cooler, and the liquid heat medium preheated by the second tar cooler is introduced into the first tar cooler, A method for recovering heat from tar-containing high-temperature gas, characterized in that a liquid heat medium heated in a tar cooler is further heated by introducing it into a high-temperature spouted bed cooler.